The US President laid into his allies over their military spending on the eve of the NATO summit, which is likely to raise concerns about the future of the 28-member coalition.
Donald Trump has repeatedly hinted he may withdraw US support for NATO altogether, calling it obsolete and a waste of American taxpayers’ dollars.
He said many countries were “nowhere close” to their commitment to spend two percent of GDP own defence.
Writing on Twitter, he said: “The United States is spending far more on NATO than any other Country. This is not fair, nor is it acceptable.
While these countries have been increasing their contributions since I took office, they must do much more.
"Germany is at one percent, the US is at four percent, and NATO benefits.”
He also again attacked Brussels for having a trade surplus with the US adding “big Trade Barriers on US goods. NO!”
Germany is also under pressure from Mr Trump to pay its fair share as, according to NATO statistics, it only spends 1.2 percent of GDP on defence - considerably less than the two percent mutually agreed by the alliance’s member states.
The Republican firebrand leader added: “Europe far more than it does the US By some accounts, the US is paying for 90% of NATO, with many countries nowhere close to their two percent commitment.
“On top of this the European Union has a Trade Surplus of $151 Million with the U.S., with big Trade Barriers on US goods. NO!”
The strongly-worded rant is the latest criticism of NATO by Mr Trump and will set the ball rolling for a tense showdown with EU leaders on Wednesday.
The defence alliance already relies heavily on Washington for around three-quarters of its funding.
In Europe, many still do not meet the two per cent of GDP target set by Nato - although Britain does.
Relations between Brussels and Washington are already at an all-time low after the US leader slapped tariffs on steel and aluminium EU goods.
It comes after a think-tank warned Britain needs to increase defence spending by 50 percent to convince Me Trump to continue to back NATO.
Think-tank Policy Exchange said there is “no viable successor to Nato as guarantor of European security”.

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